1. Field of the Invention
The present invention generally relates to connectors, and more particularly to an electrical interconnection for a card or printed circuit board along its edge.
2. Description of the Related Art
Many modern electronic devices and systems have a printed circuit board (PCB, also referred to as a printed wiring card) or similar planar substrate that is used to physically support circuit structures such as discrete electrical elements (resistors, capacitors, etc.) and integrated circuit chips (microprocessors, digital signal processors, etc.). A PCB also provides features for interconnecting these structures with one another or with external components. A typical PCB has signal traces or tracks formed on one or both surfaces (top and bottom) using a conductive material such as copper, with contact pins, tines, sockets, pads or strips at terminal ends of the traces (connection points). Components may be adhesively bonded or mechanically fastened to the PCB, and electrical connections may be completed using various technologies such as solder balls (e.g., controlled collapse chip connection, or “C4”) or surface mount technology.
Computer systems in particular usually have a primary PCB referred to as a motherboard which supports the main system components (e.g., microprocessor(s) and memory) as well as ancillary components, and often have several other PCBs. Separable extensions of the motherboard are commonly referred to as a daughterboard. Specific functionalities can optionally be added in some computer systems using expansion cards having standardized connectors such as PCI (peripheral component interconnect) or ISA (industry standard architecture). Daughterboards are sometimes used in computers as an intermediate PCB to allow expansion cards to fit parallel to the motherboard, in order to maintain a smaller form factor, in which case they are also called riser cards, or risers. Other forms of PCBs may additionally be used, such as a midplane that allows daughter cards to be connected on both sides of the midplane, and can route signals between daughter cards connected on the same side or can cross-connect a daughter card on one side of the midplane with a daughter card on the other side.
As electronic devices become more complicated, it becomes increasingly difficult to provide optimal interconnections between all of the components, particularly the motherboard which acts as a central hub for all of the computing activity. These systems are further experiencing increases in packaging density while requiring improved signal bandwidth and performance. There is accordingly a need to reduce packaging size and increase the signal density with in the packaging systems. This issue becomes more critical at the edges of a printed wiring board where a large number of signals may need to escape to create a computational network with other processes, interface with storage devices, interface with customer devices, etc. One interconnection solution 10 is depicted in FIG. 1. In this design, additional connector interfaces are employed to provide the necessary physical space translations to interconnect the required electronic assemblies along a single edge of the motherboard 12. A first edge connector 14 is disposed at the motherboard edge, mounted on the bottom side. Edge connector 14 provides one set of lateral connections for this edge of motherboard 12. A first right-angle connector 16 is attached to the top surface of motherboard 12, and provides a set of connections to a vertically-disposed intermediate board (riser) 18. As used herein, the term “right-angle connector” generally refers to connectors adapted to interconnect two boards which are perpendicular to one another, although it may describe other connections where one connection interface is vertically disposed while the other connection interface is horizontally disposed, without regard to the board orientations. A second right-angle connector 20 routes this set of connections from riser 18 to another intermediate board 22 which extends horizontally from riser 18 in the same direction as the edge of motherboard 12. A second edge connector 24 mounted on intermediate board 22 provides the second set of lateral connections for this edge, to interconnect with another edge connector 26 mounted on a daughterboard 28.